The present invention relates to a mobile communication terminal apparatus which makes data communications using a cellular mobile communication network system with a CDPD (cellular digital packet data) service function.
As one of the communication services provided in the cellular mobile communication network system, a CDPD service is known. In the CDPD service, a base station or cell site for CDPD is equipped in addition to a base station for an existing cellular mobile communication network system such as AMPS (advanced mobile phone service system), and a data communication terminal such as a personal computer is used. An idle channel is searched from radio channels for voice communications, and is assigned as a data communication channel to a mobile station that requests data communications, thus allowing mobile data communications. Upon using radio voice channels, voice communications have priority. More specifically, when an arbitrary radio voice channel is used in data communications, if another mobile station attempts to start voice communications using that radio voice channel, the CDPD base station and the mobile station release the radio voice channel in use. Then, another unused radio voice channel is searched for, and mobile data communications are continued using the found radio voice channel.
The CDPD function has the following features.
(1) The RF resources of the existing cellular mobile communication system, and the station office, antenna, and approach line of the base station can be commonly used, resulting in low cost.
(2) Seamless communications can be provided by performing channel switching and roaming during communications.
(3) The CDPD supports TCP/IP (transmission control protocol/inter-net protocol) as the host protocol in computer network communications, and can provide a connection-less service without requiring any call connection processing.
(4) A single mobile station can attain both voice and data communications.
FIG. 26 shows the schematic arrangement of a cellular mobile communication network system with the CDPD service function. This system comprises a plurality of mobile data intermediate stations DIS1, DIS2, . . . connected to intermediate stations IS of a cable network, and makes up sub-networks in units of mobile data intermediate stations DIS1, DIS2, . . . . Each sub-network corresponding to, for example, the mobile data intermediate station DIS1, is built by data communication base stations or cell sites DBS11, DBS12, . . . respectively set in cells E11, E12, . . . , and a plurality of data communication mobile stations DMS11, DMS12, . . . connected to these data communication base stations DBS11, DBS12, . . . via radio channels.
The mobile data intermediate stations DIS1, DIS2, . . . exchange data between the plurality of data communication base stations DBS11, DBS12, . . . accommodated in the own stations, and a fixed communication system or a fixed terminal FS accommodated in another CDPD system, via the intermediate stations IS. One of the intermediate stations IS has, for example, authentication, charging, network control functions, and the like.
The CDPD protocol has the following hierarchical structure. FIG. 27 shows that structure. Referring to FIG. 27, the data communication mobile stations DMS1, DMS2, . . . and the data communication base stations DBS1, DBS2, . . . are connected via the physical layer and the MAC layer. The MAC layer defines data transparency, frame encapsulation and error detection/correction functionality such as frame synchronization, radio access collision control (DSMA-CD: slotted non-persistent digital sense multiple access with collision detection), timing control based on synchronous words, and the like.
The data communication mobile stations DMS1 and DMS2, . . . and the mobile data intermediate station DIS are connected via the MDLP (mobile data link protocol) layer and the SNDCP (sub network dependent convergence protocol) layer. The MDLP layer corresponds to link control unique to CDPD, and defines a sleep mode for battery saving of hand held phones. The SNDCP layer provides a function of absorbing differences between the IP or CLNP layer corresponding to the network layer of the fixed terminal FS connected to a cable network NW, and the above-mentioned MDLP layer. The SNDCP layer multiplexes or distributes data from different SAPs (service access points) and compresses/expands a long protocol header of the network layer to improve the use efficiency of radio channels.
Each of the data communication mobile stations DMS1, DMS2, . . . comprises a hand held phone HHP, a personal computer PC, and a modem unit MU connecting the hand held phone HHP and the personal computer PC. Note that reference symbol CC denotes a curl cord for connecting the modem unit MU and the hand held phone HHP.
The personal computer PC has the control function on the mobile station side for CDPD communications. That is, when a CDPD mode is set, the personal computer PC connects the hand held phone HHP and one of the data communication base stations DBS1, DBS2, . . . via a radio channel in accordance with a predetermined CDPD protocol, and thereafter, performs data transmission control. At that time, the modem unit MU performs various interfacing operations required for radio-transmission of data transmitted by the personal computer PC via the hand held phone HHP.
However, in the conventional data communication mobile station, measurement data such as received signal strength information (RSSI: Received Signal Strength Indicator) and the like obtained by the hand held phone during setting of the CDPD mode are not displayed on the personal computer. For this reason, upon looking for a location where the radio wave reception state is good, the operator must operate the personal computer while observing the RSSI measurement data displayed on the display unit of the hand held phone. In contrast to this, when a CSCD (circuit switched cellular data) mode in which the hand held phone executes control associated with radio connections in place of the personal computer is set, status information of the personal computer is not displayed on the hand held phone at all. For this reason, the operator must perform operations for radio connections at the hand held phone while observing the display unit of the personal computer.
More specifically, in the conventional data communication mobile station, various kinds of control information generated by the hand held phone and personal computer are merely displayed on the hand held phone or personal computer as the generation source. For this reason, even in communications in the CDPD mode or in radio connections in the CSCD mode, the operator must operate while observing the display unit of the hand held phone or personal computer, resulting in poor operability.